Multiple run drier



Jan. 11, 1966 H. 1.. SMITH, JR 3,228,114

MULTIPLE RUN DRIER Filed Nov. 14, 1962 5 Sheets-Sheet 1 INVENTOR Horace L. 5mifh,Jr

ATTORNEYS Jan. 11, 1966 H. L. SMITH, JR 3,228,114

MULTIPLE RUN DRIER Filed Nov. 14, 1962 5 Sheets-Sheet 2 INVENTOR Horace L. Smith, .Jr.

ATTORNEYS H. L. SMITH, JR

MULTIPLE RUN DRIER Jan. n, 1966 5 Sheets-Sheet 5 Filed Nov. 14, 1962 INVENTOR Horace L.$mifh,./z

Jan. 11, 1966 1.. SMITH, JR

MULTIPLE RUN DRIER 5 Sheets-Sheet 4.

Filed Nov. 14, 1962 ya w EN v EN N5 mow INVENTOR Horace L. Smith, Jr.

Wfiyfl ATTORNEYS Jan. 11, 1966 H. L. SMlTH, JR 3,228,114

MULTIPLE RUN DRIER Filed Nov. 14, 1962 5 Sheets-Sheet 5 ff 4 INVENTOR Horace L. Smith, Jn l0 0 J ATTORNEYS United States Patent 3,228,114 MULTIPLE RUN DRIER Horace L. Smith, Jr., Richmond, Va., assignor to Hupp Corporation, Cleveland, Ohio, a corporation of Virginia Filed Nov. 14, 1962, Ser. No. 237,586 8 Claims. (Cl. 3452) This invention relates to the heat treatment of web and sheet materials, and more particularly to drying continuous paper web and pulp sheet. Description of this invention will therefore be made in connection with pulp paper drying, it being understood however, that it may have general application to the drying, or heat treating, of web or continuous sheet materials.

In the manufacture of paper pulp sheet and paper most drying is presently carried out today by passing newly formed paper web over large steam heated drum driers. The disadvantages of these drying systems are numerous, but foremost is the expense involved. A large paper machine, using 60 inch diameter driers with a trim width of 200 inches, may employ as many as 100 or more of such driers each presentingly costing $15,000 to $25,000.00 installed in the machine. Paper shrinks as it dries. This necessitates driving the drums in sections with a very complicated control arrangement to compensate for dimensional changes in length as the sheet dries, by gradually changing the rotation speed of the driers progressively throughout the length of the machine. Even with the most sophisticated controls, tension accumulates in the sheet causing frequent breaks resulting in immediate loss of material and time until all of the break is cleared out and the machine started in normal production again. One reason for these frequent breaks is that the distance the sheet moves between two adjacent driers known as the draw, is very short thus afiiording no margin or slack to enable the sheet to flex.

Another serious disadvantage of the present conventional steam heated rotary driers is the difficulty of removing the condensate from these driers at higher operating speeds. A 60 inch drier rotating at a surface speed of 2000 feet per minute develops 14g; therefore, one pound of condensate exerts a radial force of 14 lbs. and acts as a centrifuge causing the condensate to form a diflicult to remove hollow cylinder of water inside the drier. The condensate thermal conductivity being only & of carbon steel, causes a very high temperature gradient from the condensing temperature of the steam to the drier outer shell temperature. Paper manufacturers are today leaning toward faster machines, capable of producing paper at speeds in the order of 3000 feet per minute. Since centrifugal force varies 'as the square of the speed, increased operating speeds exaggerate the condensate problem. The present invention is capable of operating at such speeds, or higher, without the frequent sheet breaks and other disadvantages of the slower prior drum drier systems. Briefly, this is accomplished by providing a drier system characterized by long horizontal runs with the sheet supported directly by separated idler rolls without supporting conveyor belts and heating by radiating panels which permit higher operating temperatures with substantially increased speed and production capabilities and with improved paper quality. My improved arrangement provides much more flexibility for the give and take of the sheet, greatly reduces initial machine and setting up costs, frequency of breaks and down time, and operating and maintenance costs. To obtain the full benefits of the high speed horizontal runs, the supporting rolls are preferably displaced vertically relative to each other to provide compensating paper chordal arch runs that minimize high speed sheet flutter.

The most pertinent prior art of which I am aware is US. Patent No. 1,432,729 to Pinder which discloses a 3,228,114 Patented Jan. 11, 1966 multiple run paper drier in which conveyor belts supported vertically on displaced rollers, support the paper in separate runs which interfere with the drying efiiciency, utilize relatively inefficient heating means, and differ in other important respects from my improved apparatus and methods which achieve high speed production of improved paper quality. Thus, while Pinder discloses superficial preliminary drying, conveyor belt support is required in the subsequent drying and relatively low speed pressing and iron ing rollers are required at the beginning and end of each run. In my invention preliminary drying produces a self-supporting sheet supported solely by spaced direction changing, tension and speed controlling rollers, and efiiciently heated on both sides throughout the drying runs. Further, Pinder dries in closed casings in each run, introducing dry air at one end and sucking it out the other. The vapors entrained in the casings are kept in close contact with the web throughout each run to the extent that heaters are not utilized in about the first one-third length of each run. The present invention on the other hand speeds the drying operation by utilizing relatively high temperature radiant heat applied to quickly volatize the moisture or other volatiles in the sheet without overheating of the paper and removing the volatiles rapidly from the drying area.

I have further discovered that paper and the like sheet material may be heat treated without formation of a large number of wrinkles by the use of a plurality of relatively small support rolls to provide a correcting influence in ironing out wrinkles in the sheet. This is due to the fact that such correcting occurs at the first point of tangency as the sheet begins to curve around the roll. Therefore, even though the angle of contact is small between the sheet and each support roll in the slightly curved row of support rolls, the correcting influence of the small diameter support rolls is much greater than if a large amount of wrap around large rolls is permitted to exist, as would be the case in conventional horizontal run apparatus. Moreover, in such conventional apparatus only the end rolls create an angular change in travel direction. -F0r example, in the above cited Pinder patent, although a plurality of support rolls is shown, the sheet material travels in a straight line from the end to the middle of each run whereas, in accordance with this invention each support roll may create change in the direction of sheet travel which dissipates or counteracts the forces tending to wrinkle the sheet. The are of contact between the paper and the roll is of no importance because all of the correcting effect takes place at the instant of sheet contact with the roll.

Accordingly, it is a primary object of this invention to provide improved high speed relatively low cost pulp and paper drying methods and apparatus for producing improved quality paper and like products.

Another object of this invention is to provide improved multiple run pulp and paper drying methods and apparatus utilizing relatively high temperatures at faster speeds than heretofore, and comprising a preliminary drymg phase in which the paper is dried sufiiciently to be self-supporting in a multiple run drier, followed by multiple run drying under atmospheric or sub-atmospheric conditions at speeds controlled to compensate for shrinkage in each run.

A further object is to provide improved multiple run paper drying and pulp sheet drying apparatus and systems having a plurality of relatively long substantially horizontal runs arranged to prevent substantial fluttering of the sheet during high web operation while exposing the paper to relatively high temperatures, and conveying the paper without damage at high speeds while drying.

Still another object of the present invention is to provide a novel method and apparatus for heat treating flexible sheet material in a single or multiplicity of runs, which material is susceptible to wrinkling, or otherwise undesirably deforming, said method comprising conveying the flexible sheet over a plurality of relatively small support rolls such that the direction of sheet travel is changed at least slightly to exert a correcting influence on the forces tending to wrinkle or cockle the sheet material.

Other objects are to provide such improved systems and apparatus with (a) automatic web tension sensitive means for regulating the speed of the sheet pulp, paper and other sheet and web materials at various points along their path of travel, (b) radiating panels operating at relatively high temperatures and located on opposite sides of the sheet, and (c) novel direction changing rolls (heated or unheated) which may be utilized to move the paper sheet through the drying system.

Still further objects and advantages of the present invention will become apparent to those skilled in this art from the appended claims and following description of the preferred mode of carrying out this invention taken in connection with the accompanying drawings wherein:

FIGURE 1 is a diagrammatic front elevation illustration of a multiple run sheet pulp and paper drying system embodying the principles of this invention, the horizontal runs being relatively long but broken to enable enlargement of the illustration;

FIGURE 2 is an enlarged front elevation view of a sheet direction changing roller utilized at the end of each run as illustrated in FIGURE 1;

FIGURE 3 is a detailed diagrammatic illustration of a tension sensing device employed in the multiple run system illustrated in FIGURE 1;

FIGURES 46 diagrammatically illustrate another embodiment of this invention in which currents of gas are directed along one or both surfaces of the sheet material. FIGURE 4 is a digrammatically illustrated plan view of the preferred apparatus utilized in accordance with the embodiment of the invention. FIGURE 5 is a side elevation view of the apparatus illustrated in FIGURE 4. And, FIGURE 6 is a fragmentary enlarged front elevation View of a portion of the apparatus illustrated in FIGURES 4 and 5 taken between lines 6A and 6B of FIGURE 5;

FIGURE 7 is a diagrammatic side elevation view of a further embodiment of this invention in which multiple run paper drying may be carried under sub-atmospheric pressure;

FIGURE 8 is an enlarged side elevation detail of an inlet; or outlet, device utilized in the apparatus illustrated in FIGURE 7;

FIGURES 9, and 11 illustrate conventional drying apparatus. FIGURE 9 is a side elevation view of a multiple drum drill. FIGURES 10 and 11 are vertical sections taken along lines 1010, and 11l11 of FIG- URE 9;

FIGURE 12 is a side elevation view of a sheet of material passing over a plurality of rollers according to the preferred embodiment of this invention; and

FIGURES 13, 14 and 15 are diagramamtic end views of rollers, FIGURES 14 and 15 having sheet material in contact therewith.

In the preferred arrangement (FIGURE 1) for carrying out the present invention, a more or less conventional initial drying system is utilized to prepare newly formed pap-er 10' produced, for example, by Fourdrinier or British Inverform equipment for drying on the multiple run system. For purpose of illustration after the water has drained by gravity from the furnish, which is a dilute slurry of water and fiber and formed as a sheet of interlocked fibers on a wire mesh belt 14 in the Fourdrinier, the wire belt and fiber sheet are passed over suction boxes 16, and air is caused to flow downward through the sheet, wire belt, and into the suction box which is usually maintained at from 6 to 10 inches of mercury vacuum. Thereafter, it is passed over a vacuum couch roll 18, and then through presses 20 and 22. In accordance with this invent-ion, preliminary drying is then begun on, for example, heated drier rolls 26. This prelimanry drying is regulated to dry the paper leaving rolls 26 so it is capable of supporting its own weight between relatively widely spaced rolls in the multiple run system without breaking when traveling at a high rate of speed.

An idler roll 28 conducts sheet 10 onto a series of support rolls 32 in the multiple run drying apparatus of this invention. The support rolls (spaced substantially uniformly along each run) are positioned to form a very slight chordal arch in the sheet. Each support roll 32 will therefore receive a downward vertical component of force from sheet 19 and vertical flutter of the sheet at high speeds will be avoided.

Sheet 10 is passed between radiator elements 34 and 36 located above and below the sheet respectively. Radiators 34 may be a continuous platen having fluid channels therein permitting circulation of a heated fluid to achieve the desired temperature development in sheet 19. Radiators 36 are preferably separated panels located one each between each pair of adjacent support rolls 32, However, they may also be a continuous platen similar to radiators 34. A suitable arrangement for effecting circulation of heat exchange fluid heated to about 450700 F. through the radiators is illustrated in my copending application Serial No. 166,182 entitled Heating, Drying and Curing Apparatus and Methods filed January 15, 1962 and reference is hereby made to said copending application for .a complete description of a heat exchange fluid circulating system and also for details of the radiating platens, fluid circulated therein, and for means adapted to rapidly remove vapors from the drying zone. Briefly, it is preferred that the latter be accomplished by forcing ventilating streams of gas along the surface of the paper in either the same or opposite direction of paper movement. However, cross ventilation is also very effective. A suitable cross ventilation system in which air is directed at a right angle to the direction of sheet movement is also disclosed in my copending application Serial No. 166,182. The gas streams, particularly those directed longitudinally of the paper, scour the sheet material and quickly remove vapors from the immediate area of the sheet surfaces. After heating and formation of the vaporous substances, later or continued vapor contact with the sheet which might impede rapid drying is thereby prevented.

It is preferred, although not necessary, that the faces of the radiators 34 and 36 facing sheet 10 be treated with lamp black, a dark blue or black glass frit, or other suitable material capable of enhancing the radiation emissiv-ity characteristic of the platens. The temperature of the platens is preferably regulated to supply radiant energy having a peak wave length corresponding to the wave length of heat radiation most efliciently absorbed and converted into heat by sheet 10,

For ease in reference, the substantially horizontal runs are labelled as levels 1-5 from top to bottom as indicated in brackets in FIGURE 1. The horizontal runs, and the self-supporting sheet, permit relatively longer continuous runs which may be constantly heated without Interruption of frequent direction changes as would be necessary in a vertical, multiple run arrangement in which tension quickly builds up to an unbearable degree in the paper due to the paper, and moisture content weight.

Between levels 1 and 2 on the right-hand side of the multiple run apparatus as viewed in FIGURE 1, a driving roll 38 receives sheet 10 and changes its direction and drives it through level 2. Drive rolls 40, 42, 44, and 46 are likewise positioned between successive levels respectively and adapted to change the direction of sheet 10 and drive it into the next adjacent level. The drive rolls may be heated by the heat exchange fluid if desired although such is not necessary.

In FIGURE 2, a close up of a drive roll is illustrated, for example, drive roll 38. The roll is a substantially hollow cylindrical element which may have channels in the wall thereof for passage of heat exchange fluid therethrough if it is desired to heat the drive roll. Felt 50 or other suitable material is strung over four rollers and adapted to engage and press sheet against roll 38. Felt 50 is driven by a pair of drive rolls 52 over idler rolls 54 and by a drive chain or belt 56 strung over a suitable drive pulley 58 extending from the side of roll 38 around drive pulleys 60 on each of the driven rolls 52 and around tensioning rolls 61. Felts 50 are illustrated as urging sheet 10 against each of rolls 38, 40, 42, 44, and 46. However, depending upon the strength of the particular sheet material being dried one or more of the latter felts may be eliminated. The felt increases pressure normal to the surface of the driving rolls and thereby develops more driving force for the sheet without increasing tension in the latter, The felt also serves an important function in high speed machines in that the sheet traveling at speeds of from 2000 to 5000 feet per minute will have a great amount of inertia and will tend to continue in a straight line, pulling away from the pulley. However, the felt absorbs the centrifugal force and holds the web in pulley driving contact, and is driven at the angular speed of the pulley in its area of contact with the surface of the sheet.

The drive rolls can be driven by a US. Varidyne variable frequency system at a speed equal to or slightly greater than sheet speed while the support rolls may be driven if desired by torque motors which are controlled by variable voltage devices or by motors in which the speed and torque are controlled by variable frequency current supply. The support rolls, if driven, are preferable operated at a surface speed approximately equal to, or slightly greater than that of the sheet material, so as not to change the existing tension in the sheet, either by an increase or decrease.

Sheet alignment on the rolls may be maintained by a skew roll (not shown) actuated by an edge sensing device, or by any other suitable edge guide means.

To regulate the speed of each of the individual drive rolls, tension sensing rolls (FIGURES 1 and 3) 62 are located on each of levels 1-5. By a suitable arrangement the sensing rolls are adapted to vary the speed of the drive roll to which it is adjacent thus compensating for variation in the varying degrees of shrinkage throughout the length of sheet 10.

In FIGURE 3 a more detailed illustration of a sensing roll and hook-up with a drive roll (for example 38) is illustrated. A highly suitable sensing roll 62 has been found to be a device made by Cameron Machine Company of Dover, New Jersey, current marketed under the name Web-Trol. The travel or movement of the sensing roll is controlled by the downward, vertical cornponent of force from sheet 10 resulting from tension in sheet 10 as it passes over the roll, Variations in the tension create a pressure signal which is transmitted to a control unit mechanism located diagrammatically at 64, from which a power unit is adapted to regulate the speed of the master motor driving roll 38, and may also energize valve motors 68 adapted to slow down or speed up support rolls 32. For best results the sensing roll 62 should be a highly sensitive, quick acting device with a relatively short vertical travel of only several thousandths of an inch, and in addition have low friction inertia of the moving parts in the control mechanism.

After having passed through the multiple run levels sheet 10 may then be passed through a calendering device indicated generally as 70 and collected on reel 74.

Each horizontal level, or run, should preferably be as long as practical since the longer they are the lower the cost of any particular apparatus will be. A run of 110 feet is a good minimum rule of thumb, but this will vary with the material under treatment. Production of dry sheet material may be regulated to any speed desired, but is preferably maintained between l0005000 feet per minute. For example a multiple run apparatus capable of such high speed operation may for example include 160 foot center to center drive roll spacing with five feet six inch spacing between the support rolls in levels 1, 2, and 3, and eight feet spacing between the idler rolls in levels 4 and 5 where the product is stronger and requires less support.

A five level arrangement as illustrated in the drawing having such dimensions will provide approximately 800 feet of linear drying and will expose 13,350 sq. ft. of paper to 26,700 sq. ft. of radiators enabling evaporation of approximately 44,200 lbs. of water per hour. Of course, more or less horizontal levels may be utilized depending on the product, length of the levels and operating temperatures. Smoothing or calendering rolls may also be used at various positions in the drying ap paratu to insure production of a wrinkle free, or otherwise improved finish product.

An improved embodiment of the present invention illustrated in FIGURES 4-6, involves combined scouring gas streams directed over the sheet surfaces between the sheet and radiant heater surfaces. FIGURES 4 and 5 illustrate such a multiple run paper drying apparatus comprised of a plurality of heating and ventilating sections separated in each horizontal run by a support roll 100. An individual gas circulating section of such apparatus is illustrated in detail in FIGURE 6.

A longitudinally tapered air inlet manifold 104 as shown in FIGURE 4 is adapted to supply air to a plurality of substantially vertically arranged inlet plenums 108 (FIGURES 5 and 6) located in each run of each section of the drying apparatus. A blower 112 (FIGURE 5 is connected with and supplies air or other gas to inlet manifold 104 under sufficient pressure to force it longitudinally over the surfaces of paper sheet 114 alternately counter to and with the direction of sheet movement between the radiating and sheet surfaces, into exhaust plenums 116 (FIGURE 6) disposed opposite such inlet plenum 108 in each run section. The air is collected from the various outlet plenums 116 in a longitudinally tapered exhaust manifold 132 and recirculated therethrough to blower 112 which forces a predetermined percentage out through exhaust valve 118, and returns the remainder to the dryer. If desired, the inlet and exhaust plenums may be arranged to cause the gas to flow counter to the movement of sheet surface throughout.

Fresh air outlet and inlet valves 118 and 120 are controlled so that a desirable humidity level of the air is maintained. An air heater 124 is provided in the system between blower 112 and inlet manifold 104 to heat the air to the desired temperature, and may be of any suitable design.

The individual paper runs of this embodiment are essentially the same as those illustrated in FIGURE 1 in that they are slightly curved and preferably controlled at the ends by a felt or other suitable belt arrangement indicated generally as 136, which is preferably of the type illustrated and described in connection with FIGURE 2 above.

As shown in more detail in FIGURES 5 and 6, a section of the multiple run drying apparatus illustrates the slightly curved path of sheet material 114 supported on support rolls and passing alternately in opposite directions a indicated by the arrows. Radiators 144 are secured both above and below, and spaced approximately the same distance from the paper. Inlet plenums 108 are provided with an upper and lower nozzle 143 and 152, respectively, which extend over the width of paper 114 and are adapted to direct the air, through the space confined between the paper and radiator panels 144, substantially parallel to and in contact with the paper sheet surface-s longitudinally with respect to the sheet. Exhaust or outlet plenums 116 are similarly provided with an upper and lower receiving nozzle 156 and 160, respectively. The upper and lower inlet and exhaust plenums are provided with only one nozzle.

In a further embodiment of this invention illustrated diagrammatically in FIGURE 7, a multiple run drying apparatus essentially as shown in FIGURE 1 and which therefore will not be described again, is shown housed in a suitable drying chamber 290 preferably designed to withstand full atmospheric pressure on the outside with sub-atmospheric pressure inside, for example, pressure at or near zero.

A vapor off-take 204 is located in any desirable position and is connected with a condenser 208 and condensate removal pump 212.

Inlet and outlet openings 213 in the chamber are provided with sealing devices for example, of the type illustrated in detail in FIGURE 8 to prevent substantial loss of pressure differential between the chamber interior and exterior. The sealing devices comprise a pair of rollers 214 biased toward each other and pressed into sealing engagement with opposite sheet surfaces by springs 218. Sealing spring metal covers 222 are provided on the exterior chamber wall which press resiliently into tangential sealing engagement with the periphery of rollers 214.

Water vapor absorbs radiant energy, the rate being related to the thickness of the space between the paper and radiator, and the concentration of the water vapor. By maintaining the thickness at about 6 inches maximum, and the concentration low and by maintaining sub-atmospheric pressure in the chamber, this absorption will be minimized. At 28 inches vacuum, which is 2 inches absolute '(Hg) with no air present, the density of water vapor will be approximately of what it would be at atmospheric pressure. And the sub-atmospheric environment will result in moisture release from the paper of pulp at a much faster rate than at atmospheric pressure.

FIGURES 9-'l5 illustrate the principles involved in eliminating wrinkling in accordance with this invention. In FIGURES 9, :10 and 11, a conventional arrangement is shown wherein sheet 25f is passed around a series of heated drums 254, 258, 262, 266 and 270. A felt 274 driven around rollers 278, is adapted to press the sheet material against the exterior surface of the upper drum members 258 and 266.

Elasticity of the sheet will enable it to elongate in the direction it is stressed. Force vector directions are indicated by arrows 286 in FIGURE 11. These forces are developed primarily in the draw sections between the 'drums, i.e., the straight run of the paper or like material between adjacent tangent points on two successive drum driers, and are at right angles to the direction of elongation thereby tending to cause sheet width reduction, and eventual wrinkling or corrugation as shown in FIGURE 10. In the case of thin sheet material 250, stiffness resisting edgewise compression is small.

To iron out or prevent wrinkles or cockles, it is necessary to have normal directed forces acting on the surface of the drier to force the wrinkles out and make the sheet lay flat on the surface of the drier. The present conventional method of accomplising this result is by using felts, such as belt 274, which can be stressed much more than paper sheet to create substantial pressures normal to the drier surface.

In accordance with a further embodiment of my invention, radiant heaters, between which the web to be dried is passed, are preferred to effect high speed drying which precludes use of radiation intercepting paper ironing felt. I have discovered that ironing may be effected more efliciently by passing the paper over spaced relatively small rollers arranged to alter the web direction slightly over the rollers while subjecting the web to radiation and heated air or gas streams as hereinbefore described.

In explanation of the substantially increased wringle correcting influence exerted by the smaller rollers, reference is made to FIGURES 13, 14 and 15. FIGURE 13 shows 8.. a cylinder subjected to internal pressure, a compressed air tank for example. The stresses in the shell are determined by taking the pounds pressure per square inch times the diameter. This total force is equalled by the stress in the shell, and as there are two thicknesses. of shell through any 'diametrical section, the stress in one thickness of shell is equal to the pressure times the radius.

Conversely, a given stress in the shell divided by the radius gives the pressure per square inch and this pressure is the same, regardless of whether the shell wall is a closed cylinder as in FIGURE 13 or is a section of flexible sheet material contacting a roller as illustrated in FIGURES 14 and 15, and includes only a very small angle of curvature.

Depending upon the material characteristics certain minimum pressures are required to smooth out the wrinkles in a web or sheet. Therefore the smaller the diameter of the supporting roller, the less tension required in the sheet to develop equal pressure normal tothe surface. With less tension required in the sheet, less forces such as illustrated at 286 in FIGURE 11 are developed at right angles to the run of the sheet. The principles involved are illustrated in the following example and equation. For a circular curved Wall as illustrated in FIGURE 13,

F =PR where:

F=hoop tension P=internal unit pressure R=cylinder radius P, normal to the sheet surface when in contact with a cylinder is therefore inversely proportional to the radius and directly proportional to the tension in the sheet. As an example, assume a cylinder 60 inches in diameter and a stress in the paper of 1 pound per linear inch; the pressure normal to the surface is of a pound per square inch. But, if the cylinder is 8 inches in diameter and 1 pound per linear inch stress is maintained in the sheet, the pressure normal to the surface is Mr pound per square inch or 7 /2 times as much as may be obtained under the same conditions Wlfll'l a 60 inch diameter cylinder.

Thus, instead of using conventional 60 inch diameter drier units, I utilize rollers such as 32, 62 or shown in FIGURES l and 3-6, and 12 and 14; the material characteristics of which depend upon the width of the web and the permissible axial roller deflection under operating stresses. By way of example, for a paper web width of 200 inches roll diameters of the order of 8 to 12 inches are preferably used. By regulating the speed at which the rollers are driven in response to tension sensing dGVllCCS as discussed in connection with FIGURE 3, the web stresses my be minimized and maintained substantially uniform throughout the drying operation with substantially decreased web breakage and resulting down time and costs and improved quality compared to the conventional paper drying operation down time, costs and product quality.

I have also discovered that the wrinkle correcting influence imparted by the surface of a roller to a paper sheet is not dependent on the angular extent of contact, and that it is therefore dwirable, in addition to using small rollers, to provide as little contact with each roller in a horizontal run as possible. Wrinkle correction occurs at the for-wand tangent point as the sheet starts to assume a curved shape about the roller. The correcting influence is therefore probably a function of the ratio between the length of the inner surface and length of the outer surface of the sheet which for any given diameter roller will be substantially the same for various arcs of contact, but will vary greatly between large and small diameter rollers. Thus, as shown in FIGURES 14 and 15, the ratio of sheet surface length not in contact with the roller, and the length of that surface contacting the roller, will be approximately the same between angles A and B, but would be different for a like angle in a larger roller. To secure maximum wrinkle removal in a web I therefore preferably vertically displace the axis of each supporting roller a slight amount with respect to the axis of the preceding web supporting roller as illustrated in FIGURES -7 to provide a slight Web or sheet wrinkle correcting directional change in passing over each supporting roller 32, 62 and 100 and to minimize flutter of the sheet in passing over the rollers.

The invention may be embodied in other specific forms Without departing from the spirit or essential characteristics therefore. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. Multiple run horizontal type drying apparatus for continuous, moving webs of paper and like products comprising a plurality of support rolls arranged in superimposed, spaced apart, parallel, substantially horizontal rows to form a multiplicity of web drying runs, there being a plurality of said rolls in each of said rows with the centerlines of all the rollers in each of said rows intersecting a chordal arch lying in a plane normal to said centerlines, whereby adjacent rolls in each row are relatively vertically displaced to an extent sufficient to change the direction of movement of the web as it contacts each said roll and thereby prevent the formation of wrinkles as the web passes through said apparatus; drive rolls adjacent the ends of said runs for moving said web through said apparatus and for transferring the web from one run directly to the succeeding adjacent run for movement in the direction opposite that in which it travelled in the preceding run; and radiant heating means for all of said runs including radiant heaters located on both sides of the path of the web through each of the runs.

2. Multiple run drying apparatus according to claim 1, wherein said rows of support rolls are in the order of up to 160 feet long and said radiant heating means are operated at temperatures sufficiently high to dry said paper at a rate of up to 2000 feet per minute.

3. Multiple run drying apparatus according to claim 1, together with a sensing means engaging said web and means responsive to the sensing means for individually regulating the speed of each of said drive rolls to maintain a predetermined tension in the web in each of said runs.

4. Multiple run drying apparatus according to claim 1, wherein each said sensing means is a displaceable roll in contact with and responsive to variations in the tension in said web.

5. Multiple run horizontal type drying apparatus for continuous, moving Webs of paper and like products comprising a plurality of support rolls arranged in superimposed, spaced apart, parallel, substantially horizontal rows to form a multiplicity of web drying runs, there being a plurality of said rolls in each of said rows with the centerlines of all the rollers in each of said rows intersecting a chordal arch lying in a plane normal to said centerlines, whereby adjacent rolls in each row are relatively vertically displaced to an extent sufficient to change the direction of movement of the web as it contacts each said roll and therby prevent the formation of wrinkles as the web passes through said apparatus; drive rolls adjacent the ends of said runs for moving said web through said apparatus and for transferring the web from one run directly to the succeeding adjacent run for movement in the direction op posits that in which it travelled in the preceding run; and radiant heating means for all of said runs including radiant heaters located on both sides of the path of the web through each of the runs, each of said radiant heaters comprising heating elements provided with internal passages for heat transfer fluids, the sides of said heating elements which face said web having a surface coating of a material having a high emissivity coefficient to enhance their radiation emissivity.

6. Multiple r-un horizontal type drying apparatus for continuous, moving webs of paper and like products comprising a plurality of supoprt rolls arranged in superim posed, spaced apart, parallel, substantially horizontal rows to form a multiplicity of web drying runs, there being a plurality of said rolls in each of said rows with the center lines of all the rolls in each of said rows intersecting a chordal arch lying in a plane normal to said centerlines, whereby adjacent rolls in each row are relatively vertically displaced to an extent sufiicient to change the direction of movement of the web as it contacts each said roll and thereby prevent the formation of wrinkles as the web passes through said apparatus; drive rolls adjacent the ends of said runs for moving said web through said apparatus and for transferring the web from one run directly to the succeeding adjacent run for movement in the direction opposite that in which it travelled in the preceding run; and radiant heating means for each of said runs including ra diant heaters located on both sides of the path of the web through the run and a heated gas inlet plenum having a discharge nozzle positioned to direct gas from said plenum longitudinally along a surface of said web as it moves through the run, the inlet plenum for each of said runs being positioned between the run and an adjacent run.

7. Multiple run drying apparatus according to claim 6, wherein the heating means of each of said runs is provided with gas inlet plenums on both sides thereof for directing gas streams longitudinally along both surfaces of the web.

8. Multiple run drying apparatus according to claim 6, wherein said heating means each include means for exhausting said gas from said apparatus comprising an outlet plenum provided with an inlet opening positioned between the same pair of adjacent runs as the associated inlet plenum.

References Cited by the Examiner UNITED STATES PATENTS 1,432,729 10/1922 Pinder 3460 1,645,366 10/1927 Alexander 34-16 1,838,480 12/1931 Gaugler 34-155 2,067,755 1/1937 Dyer 34ll3 2,109,469 3/1938 Cohn et al. 34-24 X 2,202,045 5/ 1940 Cohn et al 3424 X 2,308,239 1/1943 Bell 34-4 X 2,517,861 8/1950 Franklin 226-42 2,605,101 7/1952 Lessmann 22642 XR 2,696,678 12/1954 Deck et a1 34-6() 3,071,866 1/1963 Mangus 34-92 3,071,869 1/1963 Latirner et a1. 34155 FOREIGN PATENTS 115,481 7/ 1942 Australia.

WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFF, ROBERT A. OLEARY,

Examiners. F. E. DRUMMOND, W. E, WAYNER,

Assistant Examiners. 

1. MULTIPLE RUN HORIZONTAL TYPE DRYING APPARATUS FOR CONTINUOUS, MOVING WEBS OF PAPER AND LIKE PRODUCTS COMPRISING A PLURALITY OF SUPPORT ROLLS ARRANGED IN SUPERIMPOSED, SPACED APART, PARALLEL, SUBSTANTIALLY HORIZONTAL ROWS TO FORM A MULTIPLICITY OF WEB DRYING RUNS, THERE BEING A PLURALITY OF SAID ROLLS IN EACH OF SAID ROWS WITH THE CENTERLINES OF ALL THE ROLLERS IN EACH OF SAID ROWS INTERSECTING A CHORDAL ARCH LYING IN A PLANE NORMAL TO SAID CENTERLINES, WHEREBY ADJACENT ROLLS IN EACH ROW ARE RELATIVELY VERTICALLY DISPLACED TO AN EXTENT SUFFICIENT TO CHANGE THE DIRECTION TO MOVEMENT OF THE WEB AS IT CONTACT EACH SAID ROLL AND THEREBY PREVENT THE FORMATION OF WRINKLES AS THE WEB PASSES THROUGH SAID APPARATUS; DRIVE ROLLS ADJACENT THE 